#define _CRT_SECURE_NO_WARNINGS 1
struct ListNode* reverseList(struct ListNode* head) {
    struct ListNode* pre;
    struct ListNode* cur = head;
    while (cur)
    {
        struct ListNode* tmp = cur->next;

        cur->next = pre;
        pre = cur;
        cur = tmp;
    }
    return pre;
}